The present invention relates generally to positive displacement pumps, and more specifically to an improved sealing arrangement for such pumps. Essentially, the sealing arrangement of the present invention is adapted for use in piston-type pumps operating under substantial pressures, with the seal arrangement including both a pressure seal and a vacuum seal to enhance the overall operation of the pump.
The positive displacement piston-type pump of the present invention is particularly adapted for use in those certain applications requiring both high pressure and high capacity. The pump, together with the sealing arrangement, is capable of accomplishing these objectives while being both light in weight and economical in construction and operation. The structure of the pump includes an open crankcase or drive housing portion which is disposed centrally of the structure, together with a pair of opposed axially aligned cylinders. The pump drive includes a drive shaft having an eccentric thereon which carries or supports a cam or drive bearing. Connecting rod means secure the cam bearing assembly to reciprocating plungers which are adapted to move reciprocably within the cylindrical sleeves.
The seals include a pressure seal assembly which comprises a generally "U"-shaped cup held between inner and outer retaining discs, with the inner retaining disc consisting essentially of polytetrafluoroethylene. The vacuum seal assembly comprises an inner guide sleeve adjacent the inner end of the cylindrical sleeve for improved guiding capability, along with an adjacent vacuum sleeve of polytetrafluoroethylene disposed outwardly of the guide sleeve. Resilent means bias the vacuum sleeve against the outer peripheral surface of the plunger. Disposed generally mid-way between the pressure seal assembly and the vacuum seal assembly is an annular groove formed within the inner periphery of the cylindrical sleeve, with the annular groove being in communication with a bore formed through the wall of the sleeve to provide constant communication between the groove and the inlet chamber of the pump. The primary function of the annular groove is to isolate the pressure seal assembly from the vacuum seal assembly so that the vacuum seal assembly is never exposed to high pressures, such as may occur when certain components of the pressure seal assembly become defective.
The concept of the present invention is an improvement over those certain piston-type pumps disclosed in U.S. Pat. Nos. 3,238,890 and 3,744,936.